The NHL club on Monday traded the pending unrestricted free-agent defenceman to Montreal for a 2015 second-round draft pick and a conditional fifth-rounder in this June’s draft.
Montreal sits atop the Eastern Conference with a 41-16-5 record.
Petry, 27, had four goals and 15 points in 59 games this season for the Oilers, who sit last in the West with an 18-34-10 mark.
Petry’s arrival will allow Canadiens all-star defenceman P.K. Subban to trim his minutes, which had soared of late with injuries to the team’s defence corps.